1. Field of the Invention
The present invention relates to apparatus for winding elongated flexible materials and more particularly to apparatus for winding a plurality of separate strips while maintaining tension in each strip. The invention may be utilized for rewinding rolled sheet after slitting to form a plurality of separate strips as well as for winding wire stock, fabric, wire ropes, etc. The present invention is preferably intended for winding a plurality of strips into coils while maintaining tension in each strip as used with cold-rolling mills.
A long-standing problem with the production of flat stock has been that of forming coils with uniform tightness and free from misalignment. The bowing inherent in the forming rolls is known to produce variation in thickness across the width of metal stripps, which variation tells on the rewinding of strips into coils, that is the material is wound with varying tension across the width of the strip and bulging of the strip relative the diameter of the winding cores develops.
When the single core-wound strip is run through a slitting operation to form a plurality of separate strips, the stresses within the strip are relieved, and in addition, the strips formed from the center portion of the single strip will have a slightly greater thickness than those strips formed from the edge portions. Thus when each of these separate strips are rewound on a common drum into separate coils, the tension in the strips forming the center coils of the drum is substantially greater than the tension in the strips forming the outer coils.
It is therefore desirable to maintain sufficient tension in each of the strips forming the separate coils during the rewinding operation so that the coils are not loosely formed and will not collapse after they are removed from the rewinding drum.
2. Description of the Prior Art
Solutions thus far proposed to overcome the foregoing problem are disclosed in U.S. Pat. Nos. 3,010,671; 3,322,361; and 3,406,924.
U.S. Pat. No. 3,010,671 teaches an apparatus for winding a plurality of strips while maintaining tension in the strips, which apparatus comprises a power-driven mandrel and drive rings and driven friction sleeves mounted on the mandrel and constituting friction pairs. The friction sleeves are provided with expansion chambers communicating with compressed air lines for positively holding the driving cores as the friction sleeves are rotated. To compress friction pairs, there is provided an air pressure arrangement. The arrangement is complicated in construction due to numerous packings and lines for supplying compressed air. Also, it is a rather complicated procedure to adjust the winding drum for a different number and width of the strips to be wound as well as to remove the coils and to prepare the apparatus for operation. It is to be also noted that the prior art apparatus is intended for and capable of winding the strips onto the cores only.
In an attempt to solve the foregoing problem there has been proposed an apparatus as disclosed in U.S. Pat. No. 3,322,361, said apparatus comprising a power-driven mandrel, friction drive disks mounted on the mandrel, and driven winding sections forming a winding drum and including cylindrical outer members supported through antifriction bearings on tubular inner members mounted freely on the mandrel. In order to readily remove the winding cores with coils thereon, the outer and inner members are built-up along their length, that is each member consists of two parts and is assembled on a single bearing. One part of the inner member is mounted freely on the mandrel, while the other is connected to a friction drive disk and is adapted to transmit axial load with the end of compressing the friction pairs. In this arrangement the procedure of preparing for operation and removal of the cores with coils is complicated insofar as a complete disassembly of the winding drum is required. This operation is carried out by hand. Since the parts of the inner and outer members are separately mounted on a single bearing, misalignment of the winding cores is quite possible which impairs accuracy in winding.
An apparatus disclosed in U.S. Pat. No. 3,406,924 also comprises a power-driven mandrel carrying drive rings and winding cores mounted for free rotation on the mandrel and adapted to frictionally engage the drive rings with their end surfaces, each of the drive rings being arranged between each adjacent pair of cores. This arrangement is also adapted to be assembled and disassembled in each coil-forming cycle. Moreover, the present apparatus is designed for winding strips onto cores only, which cores are too involved to produce, namely heavy demands are placed on the cores as regards the material, accuracy and roughness of the inner and end surfaces. Besides, a great number of cores are in circulation since coils are supplied on cores.
Also known in the art is an apparatus for winding a plurality of separate strips while maintaining tension in each strip as disclosed in USSR Inventor's Certificate No. 353,771, which apparatus comprises a power-driven mandrel having pyramidal portions with segmental members mounted on these pyramidal portions for axial movement thereon and a means for imparting such movement to these segmental members.
In this arrangement the mandrel and its pyramidal portions are made solid, therefore the segmental members forming a winding drum are rotated on the mandrel with the same speed and do not maintain equal tension in the strips, which cannot be tolerated for reasons given above.
This apparatus provides for winding strips directly onto the drum, that is without cores, since the means for axially moving the segmental members on pyramidal portions of the mandrel sets the winding drum from an expanded position (winding) to a retracted position (non-winding) due to which the operation of mounting cores is naturally eliminated.
Yet the prior art apparatus cannot be used for winding a plurality of separate strips after slitting the single wider strip because it does not provide constant tension in each strip and hence quality in coils.